Core/Shell Nanoparticles: Classes, Properties, Synthesis Mechanisms, Characterization, and Applications

A.i. in europe.

Starch is, after cellulose, the most abundant organic compound in nature. Modification of starch is carried out to enhance the positive attributes and to eliminate the shortcomings of the native starches. Various methods have been developed to produce a range of modified starches with a variety of characteristics and applications. Physically modified starches are simple and inexpensive because they can be produced without chemicals or even biological agents. In contrast, chemical modification is possible due to ubiquitous hydroxyl groups in starches that have been exploited for over a century, principally in the preparation of starch esters and ethers, but also in more subtle alterations, e.g., in order to tune the structure of starches for specific applications. All these techniques tend to alter the highly flexible starch polymer with changed physicochemical properties and modified structural attributes of high technological value for the food and non-food industries. Modification of starch is an ever evolving industry with numerous possibilities to generate novel starches which includes new functional and value added properties as demanded by the industry. This review aims to summarize the latest developments and recent knowledge regarding physically and chemically modified starches. This paper covers physical modification methods (pre-gelatinization, hydrothermal, and non-thermal processes), some chemical modifications and a combination of both.

Recent trend in the physical and chemical modification of starches from different botanical sources: A review

In recent years, due to its unparalleled advantages, the biomimetic and bioinspired synthesis of nanomaterials/nanostructures has drawn increasing interest and attention. Generally, biomimetic synthesis can be conducted either by mimicking the functions of natural materials/structures or by mimicking the biological processes that organisms employ to produce substances or materials. Biomimetic synthesis is therefore divided here into "functional biomimetic synthesis" and "process biomimetic synthesis". Process biomimetic synthesis is the focus of this review. First, the above two terms are defined and their relationship is discussed. Next different levels of biological processes that can be used for process biomimetic synthesis are compiled. Then the current progress of process biomimetic synthesis is systematically summarized and reviewed from the following five perspectives: i) elementary biomimetic system via biomass templates, ii) high-level biomimetic system via soft/hard-combined films, iii) intelligent biomimetic systems via liquid membranes, iv) living-organism biomimetic systems, and v) macromolecular bioinspired systems. Moreover, for these five biomimetic systems, the synthesis procedures, basic principles, and relationships are discussed, and the challenges that are encountered and directions for further development are considered.

Biomimetic and Bioinspired Synthesis of Nanomaterials/Nanostructures.

Chemical modification of starch by reactive extrusion

This paper describes the synthesis of long-chain fatty esters of corn starch (starch laurate and starch stearate) with a broad range in degree of substitution (DS = 0.24-2.96). The fatty esters were prepared by reacting the starch with vinyl laurate or vinyl stearate in the presence of basic catalysts (Na(2)HPO(4), K(2)CO(3), and Na acetate) in DMSO at 110 degrees C. The yellowish products were characterized by (1)H-, (13)C-NMR and FTIR. The DS of the products is a function of the carbon number of the fatty acid chain, vinyl ester to starch ratio and the type of catalyst. When performing the reactions using Na(2)HPO(4) as the catalyst, the DS for the starch laurate compounds is higher than for the corresponding starch stearates. For low vinyl ester to starch ratios, an increase in the vinyl ester concentration leads to higher product DS values. At higher ratios, the DS decreases, presumably due to a reduction of the polarity of the reaction medium. K(2)CO(3) and Na acetate are superior catalysts with respect to activity compared to Na(2)HPO(4) and products with DS values close to 3 were obtained.

/pdf/synthesis-of-higher-fatty-acid-starch-esters-using-vinyl-4a71y9uw7k.pdf

Synthesis of Higher Fatty Acid Starch Esters using Vinyl Laurate and Stearate as Reactants

Coagulation is a well-known technology applied in water and wastewater treatment. Inorganic salts, such as alum, ferrous sulfate, and polyaluminum chloride, are usually used. It is widely known that utilization of these inorganic coagulants poses several disadvantages, such as high coagulant cost and high sludge volume that increase water treatment expenses. The use of alum also poses health risk to human as it may cause degenerative diseases. In order to minimize these disadvantages, the use of various coagulants from natural resources has been recently proposed. In this research, study was performed on the extraction and use of a potential natural coagulant (Leucaena leucocephala) seed kernel as natural coagulant. Leucaena seed kernel was extracted at various NaCl concentrations (0–5 mol L−1). Extract with highest protein content obtained at NaCl concentration of 3 mol L−1 was further used to treat a synthetic wastewater model substance (Congo red solution) at various pH (2–10) and dosage (2–40 mL L−1). This natural coagulant successfully removed 99.9% of the color at pH 3 and dosage 10 mL L−1, with only half sludge volume discharged when compared to alum. The result suggests that leucaena is a promising natural coagulant for water and wastewater treatment.

/pdf/removal-of-congo-red-aqueous-solution-using-leucaena-2eq4z28z1d.pdf

Removal of Congo red aqueous solution using Leucaena leucocephala seed’s extract as natural coagulant

Synthesis of poly-(ε)-caprolactone grafted starch co-polymers by ring-opening polymerisation using silylated starch precursors

The synthesis of two reactive interfacial agents for starch-polycaprolactone (PCL) blends, PCL-g-glycidyl methacrylate (PCL-g-GMA) and PCL-g-diethyl maleate (PCL-g-DEM) is described. The compounds were prepared by reacting a low molecular weight PCL. (M(w) 3000) with GMA or DEM in the presence of benzoylperoxide (BPO) at 130 degrees C. The effect of important process variables (initiator and monomer intakes) on the functionalization degree (FD) of the GMA and DEM units to the PCL backbone was explored in detail and quantified using multivariable linear regression. The highest FD values (up to 45%) were observed for PCL-g-GMA, at relatively high GMA and BPO intakes. The FD values for PCL-g-DEM were considerably lower (up to 7%). The reactive interfacial agents were tested for their performance in starch-PCL blends. The mechanical properties of the compatibilized blends differ from the uncompatibilized ones and in particular the elastic modulus for the compatibilized blends is significantly higher. At relatively low starch intakes, PCL-g-DEM has at least a comparable performance than PCL-g-GMA. These observations may be explained tentatively on the basis of the distribution of the functional groups (GMA or DEM) along the PCL back-bone. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 23152326,2009

Synthesis and properties of reactive interfacial agents for polycaprolactone‐starch blends

This paper describes a systematic study on the synthesis of higher fatty esters of corn starch (starch laurate and starch stearate) by using the corresponding vinyl esters. The reactions were carried out in DMSO using basic catalysts (Na(2)HPO(4), K(2)CO(3), and Na-acetate). The effect of the process variables (vinyl ester to starch ratio, catalyst intake, reaction temperature and type of the catalyst) on the degree of substitution (DS) of the starch laurate and starch stearate esters was determined by performing a total of 54 experiments. The results were adequately modeled using a non-linear multivariable regression model (R(2)>= 0.96). The basicity of the catalyst and the reaction temperature have the highest impact on the product DS. The thermal and mechanical properties of some representative product samples were determined. High-DS products (DS = 2.26-2.39) are totally amorphous whereas the low-DS ones (DS = 1.45-1.75) are still partially crystalline. The thermal stability of the esterified products is higher than that of native starch. Mechanical tests show that the products have a tensile strength (stress at break) between 2.7-3.5 MPa, elongation at break of 3-26%, and modulus of elasticity of 46-113 MPa.

Asaf Kleopas Sugih

Papers

Synthesis of Higher Fatty Acid Starch Esters using Vinyl Laurate and Stearate as Reactants

Removal of Congo red aqueous solution using Leucaena leucocephala seed’s extract as natural coagulant

Synthesis of poly-(ε)-caprolactone grafted starch co-polymers by ring-opening polymerisation using silylated starch precursors

Synthesis and properties of reactive interfacial agents for polycaprolactone‐starch blends

Experimental and Modeling Studies on the Synthesis and Properties of Higher Fatty Esters of Corn Starch